1. Field of the Invention
The invention relates generally to peristaltic irrigation and distension pumps and tubing sets for use therewith. More particularly, the invention relates to an irrigation and distension pump system for surgical use, the system utilizing a tube set having a tubing cassette which holds a looped tube adjacent peristaltic rollers.
2. Description of the Prior Art
Powered pumps are frequently used in medical and surgical applications in order to pump various fluids during surgical procedures. The fluids are conveyed from a fluid source to a patient and ultimately to a fluid drain via a pump and various inflow and outflow tubes which pass fluid appropriately. Numerous system designs are known by which the tubing used with the pumps may be configured into surgical tube sets adapted for various applications (arthroscopy, laparoscopy, irrigation, etc.). The tube sets may be coded to identify the procedure for which they are designed and can be relatively easily engaged with the pump and other components. With respect to peristaltic pumps in particular, these designs generally utilize a cassette in the form of a molded housing which retains a portion of the tubing so that the engagement of the tubing with the peristaltic pump simply requires the attachment of the cassette adjacent the peristaltic pump roller assembly rather than the laborious process of threading a tube around the roller assembly and securing it in place.
One type of tubing cassette is shown in U.S. Pat. No. 5,460,490 (Carr et al.), assigned to the assignee hereof and incorporated by reference herein. This patent shows a cassette in the form of a molded block having various channels for holding a tube in a predetermined U-shaped orientation in the plane of rotation of the peristaltic pump roller assembly. The cassette is retained adjacent the roller assembly by a cam device which presses the cassette against the front panel of the peristaltic pump housing and holds the tube firmly against the roller assembly without a raceway backing plate. This device is relatively complex and requires more manipulation of the cassette than is desired in certain surgical applications. Additionally, this device requires the use of a track or race to support the tube as it engages the rollers.
Another type of “cassette” is shown in U.S. Pat. No. 5,133,650 (Sunderland et al.) in which the tubing is provided with various fixed molded components which are attachable to complementarily shaped recesses in the pump housing and a pivotable swing arm. The latter may then be swung into place in order to stretch the tube about the peristaltic pump roller assembly. This device is really a two-piece device as opposed to a one-piece cassette and is, therefore, not strictly a cassette as that term is normally understood. A similar “cassette” device is used without a swing arm in the Linvatec C7050 Irrigation Console available from Linvatec Corporation, 11311 Concept Boulevard, Largo, Fla. 33773. This device utilizes a peristaltic pump having a pump roller assembly situated adjacent fixed tube-holding stations designed to be used with a tubing set having fixed molded components secured thereto. The tubing set is used by first placing one of the molded components into one of the tube-holding stations adjacent the roller assembly, then stretching the tube around the roller assembly and securing the other molded component in the other tube-holding station. This arrangement holds the tube in generally a U-shape around the peristaltic pump roller assembly as is often done in peristaltic pumps.
Other cassette arrangements are also known in which a one-piece cassette is used with a pair of latching mechanisms in order to hold the tubing cassette in proper position adjacent the peristaltic pump roller assembly. For example, U.S. Pat. No. 5,433,588 (Monk et al) shows a cassette maintained adjacent a peristaltic pump roller assembly by the cooperative action of a pair of spaced locking surfaces, spaced on either side of the rollers. This device operates with a backing plate so that the peristaltic rollers squeeze the tube between the rollers and the backing plate. The device is relatively complex.
Another known disposable cassette for use with a peristaltic pump is shown in U.S. Pat. No. 4,537,561 (Xanthopoulos). The cassette of this device operates without a backing plate and is secured adjacent the pump by a pair of articulating latch arms which hold opposing sides of the cassette adjacent the pump roller assembly station. While this patent makes a reference to a mechanical or electromechanical arrangement utilized to release this locking mechanism, no such arrangement is shown. However, one can reasonably expect it to be relatively complex since the articulating arms must both be moved simultaneously.
Another peristaltic tubing cassette is shown in U.S. Pat. No. 5,927,956 (Lim et al.), assigned to the assignee hereof. The cassette is designed to attach a tubing set to the front panel of a pump housing having a peristaltic roller assembly rotatable in a plane parallel to the front panel of the housing. The cassette shown in this patent is a three-sided enclosure having an open bottom end. The tubing retained in the enclosure is secured on each side of the open end so that when the cassette is slid over the peristaltic rollers and latched into place, the tubing is automatically stretched around the rollers.
Cassette tube sets are easy to use and assure the proper alignment of various tubes with the pump, solenoid actuated valves, pressure sensors, etc. To further simplify a cassette type irrigation pump system, the present invention utilizes a one-sided pressure transducer.
Known prior art cassette tube systems sometimes utilize pressure sensors to provide feedback to the pump to control output pressure. Such systems often measure pressure at a point downstream and near the surgical site. These devices often utilize a separate, air filled pressure sensing line incorporating a balloon-type interface between the main, liquid filled supply tube and air filled pressure line. The liquid being pumped is on one side of the balloon and an air column is on the other side. The pressure of the liquid varies the pressure on the air column which is sensed by a transducer in the pump housing. For such systems to work the end of the tube carrying the air column must be connected to a transducer at the pump.
It is also known to sense pressure at the pump housing. For example, U.S. Pat. No. 5,044,203 (Weist et al.) shows a peristaltic pump tube set with a portion of the tube formed into a flexible tubing cushion having two (opposing and parallel) thin membranes. The cushion is designed to fit into a slot whereby the pressure exerted on the membranes (by fluid in the tube) is sensed by opposing and parallel sensors mounted adjacent to the slot. The slot is sized to closely fit the cushion in a depressurized state so that even slight pressure variations can exert small dimensional changes in the membranes which can then be detected by the sensors. One disadvantage of this arrangement is that if a user inadvertently connects a liquid supply to the tube set (i.e. “spikes the bags”) before inserting the cushion into the slot, the pressure of the liquid will have expanded the membranes to a point where the cushion will not fit into the slot.
It is also noted that some prior art peristaltic pumps operate only during the time they are below or at the pressure level called for by the control system. Once this pressure is reached, the pumps stop turning. In certain applications it would be desirable to keep the pump turning at all times to improve response time and to enable users to see that the pump is still working.
It is accordingly an object of this invention to produce a pressure transducer that may easily sense pressure in a way to avoid the disadvantages of the prior art.
It is also an object of this invention to produce a simple, disposable tubing cassette for use with a peristaltic pump roller assembly.
It is another object of this invention to produce a peristaltic pump roller tubing system which enables a tube to be engaged with a peristaltic pump roller assembly in a simple manual operation.
It is a further object of this invention to enable such a tubing cassette to be disengaged from the peristaltic pump roller assembly in a simple manual operation.
It is another object of this invention to produce a peristaltic pump roller tubing system in which output pressure may be easily measured.
It is still another object of this invention to produce a peristaltic pump roller tubing system which is capable of always providing a mechanical indication that the system is operating.